1. Field of the Invention
This invention relates to a cable connecting device, and particularly to improvements in, for example, a cable connecting device for detachably connecting a flexible cable to a component movable within a predetermined scope in a linear type displacement detecting apparatus or the like, the device comprising: a main scale mounted in an elongate case in the longitudinal direction thereof; an index scale disposed along the main scale in opposed relationship thereto in the elongate case in a manner to be movable relative to the main scale in the longitudinal direction of the elongate case; and the component (slider) provided integrally with the index scale outside the elongate case in a manner to be movable relative to the elongate case in the longitudinal direction of the elongate case; wherein a variation in the physical quantity due to a relative movement between the main scale and the index scale is converted into a length measuring electric signal by an electric circuit contained in the component (slider) to be outputted to an external component through a flexible cable.
2. Description of the Prior Art
As one of the cable connecting devices of a linear type displacement detecting apparatus for measuring or adjusting a positional relationship between two objects, there has been known a cable connecting device as shown in FIGS. 1 and 2 for example, comprising: a main scale 12 mounted in an elongate case 10 in the longitudinal direction thereof; an index scale 14 disposed along the main scale 12 in opposed relationship thereto in the elongate case 10 in a manner to be movable relative to the main scale 12 in the longitudinal direction of the elongate case 10; and a slider 16 provided integrally with the index scale 14 outside the elongate case in a manner to be movable relative to the elongate case 10 in the longitudinal direction of the elongate case 10; wherein a variation in the physical quantity due to a relative movement between the main scale 12 and the index scale 14 is converted into a length measuring electric singal by an electric circuit 18 contained in the slider 16 to be outputted to an external component, not shown, through a flexible cable 20.
Both of the main scale 12 and the index scale 14 are made of a transparent material such as glass, vertical fringe-like memories 12A and 14A consisting of optical lattices are formed on the opposing surfaces of the both scales, when a light from a light emitting element 22 at one side is transmitted through the main scale 12 and the index scale 14 and reaches a light receiving element 24 provided at the other side, bright and dark fringe patterns are generated between the memories 12A and 14A, the reading of the fringe patterns by the light receiving element 24 makes it possible to read a movement value of a work to be measured.
The bright and dark fringe patterns received by the light receiving element 24 are converted into electric signals, pass through the electric circuit 18 and flexible cable 20, and outputted to the external component, where recording and indicating are effected. Designated at 26 is a wire spring for resiliently pushing the index scale 14 against the main scale 12, 28 rollers for rotatably guiding the index scale 14 on the surfaces of the main scale 12, and 30 a cable for delivering an output signal from the light receiveing element 24 to the electric circuit 18.
Here, the index scale 14 and the slider 16 are connected to each other through an arm 32.
This arm 32 is adapted to move in a longitudinal groove 10A formed in the lower portion of the elongate case 10 as shown in the drawing during a movement of the index scale 14 and the slider 16 relative to the main scale 12. In this case, in order to prevent the intrusion of oil, dust and the like from the outside, the arm 32 is adapted to slide on a pair of seal members 34A and 34B provided on the both sides of the groove 10A, pushing the seal members open.
Thus, the elongate case 10 is isolated from the outside by the seal members 34A and 34B, so that oil, dust and the like are prevented from intruding into the elongate case 10. There have heretofore been such cases where oil, water and the like intrude into the slider 16 to adhere to the electric circuit 18 portion, whereby the electric circuit 18 is adversly affected to emit erroneous signals.
It has been found that the intrusion was caused in such a manner that the oil, water and the like were conveyed on the flexible electric wire tube formed of a mesh or a spiral tube forming an outer skin of the flexible cable 20 and entered the slider 16.
Particularly, when the scales are long, and accordingly, the scope of movement of the slider 16 is extended and the flexible cable 20 is increased in its length, oil and like are disadvantageously allowed to intrude into the slider 16, being conveyed on the outer periphery of the flexible cable 20.
In constrast thereto, there has heretofore been adopted such an arrangement that a connection box is provided at a position spaced apart from the slider 16, opposite ends of a flexible relay cable across the connection box and the slider 16 are firmly seal-bonded, and further, and end portion of a flexible cable connecting the connection box to a measuring apparatus is seal-bonded to the connection box for connection.
Nevertheless, in this case, the relay cable across the slider 16 and the connection box and the cable across the connection box and the external component are each coated by a flexible electric wire tube formed of a metal material, which is called a wire blade or so-called a metal flake (conduit cable) for the protection against damages. However, since these end portions of the wire blades are solidly secured to the slider 16 and the connection box by adhesive bonding or soldering and both the relay cable and the flexible cable are fixed similarly by soldering, such a disadvantage is presented that it becomes very difficult to replace a flexible cable with another when the length of the main scale 12 is to be changed and so forth. Furthermore, during measuring operation, a load to reciprocate the slider 16 is increased due to increased inertia because of increased weight of the connection box, and further, in order to prevent the connection box from colliding on the elongate case 10 and the like, the connection box should be moved together with the slider 16 and be supported by and fixed to a member separate of the member supporting the elongate case 10, thus presenting the disadvantages of additionally requiring increased volume and weight of the device as a whole, and the labor of mounting and sealing works.
Similar disadvantages are presented by the cable connecting device for a flexible cable to be detachably secured to a component in order to take out an output from the component which emits a signal when a touch signal probe or the like in a coordinate measuring instrument is brought into contact with a work to be measured.